Broadening of rare earth ion emission bandwidth in phosphate based laser glasses

ABSTRACT

Disclosed are the use of phosphate-based glasses as a solid state laser gain medium, in particular, the invention relates to broadening the emission bandwidth of rare earth ions used as lasing ions in a phosphate-based glass composition, where the broadening of the emission bandwidth is believed to be achieved by the hybridization of the glass network.

The invention relates to the use of phosphate-based glasses as a solidstate laser gain medium. In particular, the invention relates tobroadening the emission bandwidth of rare earth ions used as lasing ionsin a phosphate-based glass composition. The broadening of the emissionbandwidth is believed to be achieved by the hybridization of the glassnetwork.

Phosphate laser glasses are well known for use as a host matrix for highaverage power and high peak energy laser systems. See, for example,Payne et al. (U.S. Pat. No. 5,663,972) which discloses the use ofNd-doped phosphate laser glasses described as having broad emissionbandwidths. Hayden et al. (U.S. Pat. No. 5,526,369) also disclosesNd-doped phosphate laser glasses. In this case, the laser glass is saidto desirably have a narrow emission bandwidth (less than 26 nm) toimprove extraction efficiency. In this typical type of laser, theemission of the laser is narrow compared to the emission bandwidth, andthus, the emitted light at wavelengths outside of the narrow bandwidthat which the laser operates is effectively wasted. For this reason,narrow emission bandwidths are desirable.

One general trend in solid state lasers is to make high energy laserswith shorter pulse lengths, which drives the power in the pulse to veryhigh numbers. For example, a 10 k Joule laser with a 10 nsec pulselength emits a power of 1 TW (1 TW=10000 J/10 nsec). However, for highpeak power lasers using ultra-short pulses (<100 femto-second pulses orshorter), the emission bandwidth offered by known phosphate laser glassis too narrow compared to that required. To address this problemso-called “mixed” laser glass laser designs are used. Phosphate andsilicate glasses are used in series to achieve the total bandwidthrequired for current petawatt laser systems. But, the technology ofusing the mixed glasses is insufficient for future exawatt lasersystems. New broader band phosphate glass, with or without silicateglass used in series, will be required.

The trend towards the use of high energy lasers with shorter pulselengths is described in “Terrawatt to pettawatt subpicosecond lasers”,M. D. Perry and G. Mourou, Science, Vol 264, 917-924 (1994). Theselasers use a technique called Chirped Pulse Amplification (CPA) togenerate ultra-short laser pulses. To work effectively, this techniquerequires gain media with an emission bandwidth as large as possible. InTable 1, M. D. Perry and G. Mourou describe the emission bandwidths,along with pulse length and theoretical peak, for some typical solidstate laser systems.

In one aspect, the glasses disclosed herein are suitable for achievingpulselengths of less than 100 fsec and output energies above 100 kJ.

A key to short pulses is to find gain materials with broad emissionbandwidth for the laser transition. The relationship between emissionbandwidth and pulselength is: Bandwidth×Pulse Duration>=0.44. Clearly,to achieve ever shorter pulse durations it is desirable to identifyglasses with a broad emission bandwidth.

Transition metal doped crystals offer broad emission bandwidth. Forexample, the Hercules laser described in Laser Focus World, April 2008,pp. 19-20, uses Ti doped sapphire crystals.

Another way to make super short pulse length lasers is with rare earthdoped glasses. The advantages of such glasses over crystals includelower costs, higher available energies (since glass can be manufacturedin large sizes of high optical quality, while Ti doped sapphire islimited in size), and simpler designs can be implemented since the glassapproach can be pumped by flashlamps (Ti doped sapphire short pulselasers are pumped by glass lasers which in turn are pumped byflashlamps, so the glass approach does not require one to first buildpump lasers).

U.S. Pat. No. 5,663,972 appreciates the usefulness of broadband glasses.The disclosure resulted in the production of the phosphate glass APG-2,sold by Schott North America, Inc. APG-2 offers the possibility of anapproach to short pulse lasers. However, APG-2 is difficult to make athigh yields, and there is still a need for a material having even largeremission bandwidth.

A further useful commercial glass having a broad emission bandwidth andis the phosphate glass APG-1, also sold by Schott North America, Inc.For this reason, APG-1 glass can serve as a comparison example duringdevelopment of new broadband gain materials. Additionally, thecommercial glass IOG-1, a conventional phosphate glass with a narrowbandwidth emission curve, can also be utilized for comparison purposes.APG-1, APG-2, and IOG-1 doped with Nd and/or Yb are commercial laserglasses sold by Schott North America, Inc.

With respect to lasing ions, the inventors determined that Yb has abroader emission bandwidth than Nd, and as such, it may be an optimallasing ion in an exowatt laser. It was further found, for example, thatadding Yb lowered the nonlinear refractive index of the glasses of thepresent invention (see examples 1/Yb to 17/Yb and the correspondingexamples 1/Nd to 17/Nd, where in all 17 examples with Yb compared to Nd,the nonlinear refractive index was lowered), and lowered the linearcoefficient of thermal expansion of the glasses of the present invention(see examples 1/Yb to 17/Yb and the corresponding examples 1/Nd to17/Nd, where in 15 of the 17 examples with Yb compared to Nd, the linearcoefficient of thermal expansion was lowered). As such, the inventionalso relates to a method for lowering the nonlinear refractive indexand/or lowering the thermal expansion of glasses disclosed herein whichcontain Nd as the rare earth dopant, by replacing at least some of theNd with Yb, and optionally further replacing at least some of the Latherein with Yb, and optionally adding further Yb. The reason La canadditionally be at least in part replaced with Yb is that it is commonpractice to adjust the lasing ion content in a neodymium doped laserglass through the use of La, an ion that does not exhibit laseractivity. More specifically, the sum of the Nd plus La is held constant,thus as the Nd content is varied for particular applications the impacton all optical and physical properties is minimized by using La as thesubstituted ion (all of the lanthanides behave in a similar mannerwithin the glass structure).

The lower nonlinear index (n₂) means high laser energies are possiblewithout damage to the laser glass and other optical components withinthe laser system from the laser beam. This is a consequence of therefractive index of glass increasing with the intensity level of thelaser beam. As a result, when a laser beam passes through glass it isself-focused within the glass by an increasing amount with larger valuesof nonlinear index. Damage occurs when the electric field associatedwith the focused laser light exceeds the dielectric break-down of theglass, leading to the appearance of needle-like tracks both within thelaser glass and in optical components down stream from the laser glasslocation within the laser system.

The lower thermal expansion means the repetition rate of the laser canbe higher without breaking the glass from thermal shock. During use, thetemperature of the laser glass increases because a portion of the pumpenergy is converting to heat within the glass. This increase intemperature is undesirable for various reasons, including the fact thatthere is typically a reduction in the amount of laser gain as thetemperature of the gain media becomes higher (e.g. the laser glassabsorbs an increasing amount of the laser intensity). The outsidesurfaces can be cooled by air or liquid coolant but since glass is apoor thermal conductor, the inside remains hot, setting up a thermalgradient between the center of the glass and the cooled surfaces. As aresult, the glass surfaces are subjected to tensile stress, which canthen cause damage to the glass, e.g., lead to breakage of the glass bythermal shock. This tensile stress is lessened as the coefficient ofthermal expansion is lowered. So, a glass with lower expansion is lesssusceptible to damage.

However, Nd has many advantages also, for example, Nd is a four levellaser, whereas Yb is a two level laser (because of the width of theseenergy levels Yb can act somewhat like a four level laser) that makes itmore difficult to achieve laser action in a Yb doped gain media. Inaddition, because of its many absorption bands in the visible part ofthe spectrum, Nd is pumped more efficiently by flashlamps (which emit inthe same spectral region) then Yb (since Yb has only a single absorptionfeature in the infrared portion of the spectrum). However, one wayaround this problem is to sensitize the Yb with transition metals suchas Cr that have absorption bands in the visible portion of the spectrumand can transfer absorbed flashlamp energy to Yb in the gain media.

Laser properties for Nd are evaluated from an emission curve usingJudd-Ofelt theory or by a similar technique called Fuchtbauer-Ladenburgtheory. A discussion on both techniques can be found in E. Desurvire,Erbium Doped Fiber Amplifiers, John Wiley and Sons (1994). Theproperties that result include cross section for emission, σ_(em), peakemission wavelength, λ_(Peak), and radiative lifetime, τ_(Rad). One canapply this analysis to Yb as well, but because of the two level natureof the Yb laser system mentioned above, Yb absorbs and traps its ownemission light, making a precise measurement very difficult (actuallyeffectively impossible, Yb laser property results always have someinfluence from this self absorption and associated radiation trapping).

The McCumber method is another recognized technique used to get laserproperties that only uses the absorption curve of the glass, asdiscussed in, for example, Miniscalco and Quimby, Optics Letters 16(4)pp 258-266 (1991). A weakness of the McCumber technique is that it failsto give clear results where the glass has little or no absorption tobegin with, in the case of Yb this occurs at the long wavelength end ofthe emission curve. (It is an incidental point to note that the McCumberanalysis is not applicable to Nd because Nd does not have significantabsorption at any wavelength within the main emission band of interestat nominally 1 μm.)

Judd-Ofelt analysis is the preferred method and is recognized by thelaser materials community but suffers (for Yb) from this selfabsorption/radiation trapping. However, comparing the results ofJudd-Ofelt with McCumber is believed to give an indication of thereliability of the Judd-Ofelt results. This is described in L. R. P.Kassab et al., Journal of Non-Crystalline Solids 348 (2004) 103-107.After evaluation of laser properties by a complete emission curveanalysis using a technique such as Judd-Ofelt, and a second analysisusing the McCumber method and an absorption curve, a radiation trappingcoefficient (rte) is calculated. A value close to zero is an indicationthat the Judd-Ofelt analysis is not strongly influenced by selfabsorption and radiation trapping. For this reason, there are two setsof laser properties provided in the data tables for Yb containingglasses.

Regarding emission bandwidth, if one has a measured emission curve (suchas collected in a Judd-Ofelt or Fuchtbauer-Ladenburg analysis) or acalculated emission curve (from a McCumber analysis) one can getemission bandwidth in two ways. The first is to simply measure the widthat half of the maximum value (called emission bandwidth full width halfmaximum Δλ_(FWHM)=λ_(upper)−λ_(lower) where λ_(upper) and λ_(lower) arethe wavelengths where the emission intensity falls to half of its peakvalue on either side of the emission curve).

A typical emission curve for Yb is provided in FIG. 4. One can readilysee the one narrow feature at ˜980 nm. If this feature is prominent, theΔλ_(FWHM) value will only reflect the width of this one feature and therest of the curve will not contribute. In the example tables, one willnote that the Yb Δλ_(FWHM) values are either about 10 nm or about 60 nm.The smaller values are exactly this case, the larger values are whenthis 980 nm peak is not as dominant. As a result the Δλ_(FWHM) value isnot always a reliable indicator of the emission bandwidth for Yb. Nddoes not have this problem, as one can see in a typical Nd emissioncurve in FIG. 5.

The second method divides every point on the emission curve by the totalarea under the curve. The result, called a linewidth function, will havea peak value that is defined as the inverse of the effective bandwidth,Δλ_(eff). By this method the entire emission curve always contributes tothe emission bandwidth result. It is this value used herein in theanalysis as the best indicator of emission bandwidth.

Introduction of multi-oxide network formers, SiO₂, B₂O₃, TeO₂, Nb₂O₅,Bi₂O₃, WO₃, and/or GeO₂ in the phosphate predominant network can controlor broaden the distribution of lasing ion's (Yb³⁺ or Nd³⁺, for example)local chemical environments (in terms of the degrees of ligand fieldasymmetry and bond covalency). The inventors found that the networkhybridization results in rare earth lasing ion emission bandwidthbroadening.

The prior art glass APG-2 has a phosphate network. The inventors foundthat introduction of one or more oxide network forming oxides (SiO₂,B₂O₃, TeO₂, Nb₂O₅, Bi₂O₃, WO₃, and/or GeO₂) into the phosphatepredominant network in an amount of at least 1 mol % or above, e.g., 2mol % or above, broadened, or at least offered a broader distributionof, the local chemical environments (in terms of the degrees of ligandfield asymmetry and bond covalency) for lasing ion's (Yb³⁺ or Nd³⁺ forexample) in the glass. As a result, the P—O—P network is hybridized withSi—O—Si, B—O—B, Te—O—Te, etc., and the lasing ions can be dissolved inthe molten glass and be stabilized by forming bonding with differentnetwork formers. In turn, the ligand field around the lasing ions fromthe different network environments varies. As a result, under theexcitation of an incoming light source, the emission spectra of lasingions is broadened as compared with pure phosphate network glasses.

In the article “Mixed Former Effects: A Kind of Compositions AdjustingMethod of Er-doped glass for broadband amplification,” Chin. Phys. Lett.19[10] (2002) 1516-1518, J. H. Yang, et al. disclosed glasses based onTeO₂ and Bi₂O₃ systems with addition of SiO₂ or B₂O₃ to show bandbroadening comparing with silicates and phosphate based glasses thathave lower bandwidth. The article offers no insight of how to broadenthe emission bandwidth in TeO₂ and Bi₂O₃ based glasses by adding SiO₂ orB₂O₃, separately.

In U.S. Pat. No. 6,859,606B2 (Feb. 22, 2005), Er-doped TeO₂ basedglasses with and without B₂O₃, GeO₂, and WO₃ were disclosed. Bandwidthchanges were shown without explanations.

In U.S. Pat. No. 6,194,334B1 (Feb. 27, 2001), Er-doped TeO₂—WO₃ basedglasses with and without P₂O₅ or B₂O₃ are disclosed. It discusses thebandwidth broadening in terms of presence of many structural motifs thatyield a greater diversity of structural sites for incorporating dopantions (Er³⁺ in this case). The consequence of this is an enhancedsolution of effective Er³⁺ ions and broadened Er³⁺ emission spectra. Theglass system is not applicable to the phosphate system. Furthermore, noeffects of combined B₂O₃ and P₂O₅ modification to TeO₂ based glasses onbandwidth broadening are considered.

In U.S. Pat. No. 6,656,859B2 (Dec. 2, 2003), Er-doped TeO₂—Ta₂O₅ basedglasses with and without Nb₂O₅ or B₂O₃ are disclosed. The glass systemis not applicable to the phosphate system. Furthermore, no effects ofcombined B₂O₃ and Nb₂O₅ modification to TeO₂ based glasses on bandwidthbroadening are considered.

In one aspect, the laser glass compositions according to the inventionrelate to phosphate based glasses, e.g., a glass containing 35 mol % toabout 65 mol % of P₂O₅, preferably about 45 mol % to about 60 mol %,which is hybridized by the addition of at least one, optionally two,three, four or more of non-phosphate oxide network formers, i.e., SiO₂,B₂O₃, TeO₂, Nb₂O₅, Bi₂O₃, WO₃, and/or GeO₂, and doped with one or morelasing rare earth elements 58 through 71 in the periodic table, e.g.,Yb, Nd, Er, Pr, Sm, Eu, Tb, Dy, IIo and Tm, etc., preferably Yb, Nd, Erand Pr, and more preferably Yb and Nd. These rare earth elements can beused alone or in combination of one or more different ions. The sum ofone or more non-phosphate network formers is at least 1 mol %,preferably, between 1.4 to 35 mol %, more preferably between 2.0 mol %to 28 mol %. The one or more lasing rare earth elements are presentpreferably at about 0.25 to about 5 mol %.

In a further aspect, the invention relates to a glass with composition(mol %) of

P₂O₅ 35-65 SiO₂  0-20 B₂O₃  0-15 Al₂O₃ >0-10 Nb₂O₅  0-10 TeO₂ 0-5 GeO₂0-5 WO₃ 0-5 Bi₂O₃ 0-5 La₂O₃ 0-5 Ln₂O₃ >0-10 (Ln = lasing ions ofelements 58 through 71 in the periodic table) R₂O 10-30 (R = Li, Na, K,Rb, Cs) MO 10-30 (M = Mg, Ca, Sr, Ba, Zn) Sb₂O₃ 0-5and wherein the sum of the amounts of SiO₂, B₂O₃, TeO₂, Nb₂O₅, Bi₂O₃,WO₃, and/or GeO₂, is at least 1 mol %, for example, between 2 to 35 mol%, more preferably between 3 to 25 mol %, and preferably containing oneor more of SiO₂, B₂O₃, TeO₂, and/or Nb₂O₅, and where such glass has aneffective emission bandwidth, as evaluated by the lineshape functiontechnique in a Judd-Ofelt analysis, for example, of greater than 32 nmfor Nd, for example, greater than 33 nm for Nd, and of greater than 38nm for Yb, for example, greater than 40 nm for Yb or greater than 41 nmfor Yb.

Preferably, the Sb₂O₃ content is >0 to 1 mol %, more preferably 0.3 to0.4 mol %. A preferred range for Al₂O₃ content is 3.5 to 6.0 mol %,preferably 3.5 to 5.0 mol %. Also preferred is a 1.0 to 4.0 mol % ofLa₂O₃ content.

In a further embodiment, the phosphate laser glass composition is dopedwith a rare earth element as defined above, for example, Nd and/or Yb,and comprises (based on mol %):

P₂O₅ 40.00-65.00 SiO₂  0.00-18.00 B₂O₃  0.00-12.00 Al₂O₃ 2.00-8.00 Li₂O 0.00-20.00 K₂O  0.00-20.00 Na₂O  0.00-20.00 MgO  0.00-15.00 CaO0.00-5.00 BaO  0.00-15.00 TeO₂ 0.00-5.00 Nd₂O₃ 0.50-3.00 and/or Yb₂O₃La₂O₃ 0.00-5.00 Nb₂O₅ 0.00-5.00 Sb₂O₃ 0.00-2.00wherein the composition contains at least 1.00 mol % of a non-phosphatenetwork former, e.g., at least 1.00 mol % of TeO₂, at least 1.00 mol %of SiO₂, at least 1.00 mol % of B₂O₃, or at least 1.00 mol % of Nb₂O₅.More preferably, the composition contains at least 2.00 mol % of anon-phosphate network former, e.g., at least 3.00 mol %. Nd or Yb may besubstituted by other rare earth element(s) as already described herein.

In a further embodiment, the phosphate laser glass composition is dopedwith Yb, and comprises (based on mol %):

P₂O₅ 49.00-57.00 SiO₂  0.00-10.00 B₂O₃ 0.00-5.00 Al₂O₃ 2.00-6.00 Li₂O 1.00-18.00 K₂O  1.00-18.00 Na₂O  0.00-10.00 MgO  1.00-12.00 CaO0.00-3.00 BaO  1.00-12.00 TeO₂ 0.00-4.00 Yb₂O₃ 1.00-2.50 La₂O₃ 0.50-3.00Nb₂O₅ 0.00-4.00 Sb₂O₃ 0.20-0.50wherein the composition contains at least 1.00 mol % of a non-phosphatenetwork former, e.g., at least 1.00 mol % of TeO₂, at least 1.00 mol %of SiO₂, at least 1.00 mol % of B₂O₃, or at least 1.00 mol % of Nb₂O₅.More preferably, the composition contains at least 2.00 mol % of anon-phosphate network former, e.g., at least 3.00 mol %. Yb may besubstituted by other rare earth element(s) as already described herein.

According to another aspect, the phosphate laser glass compositionaccording to the invention contains 1.00-18.00 mol % of SiO₂, forexample, 1.20-15.00 mol % of SiO₂ or 1.25-10.00 mol % of SiO₂.

According to another aspect, the phosphate laser glass compositionaccording to the invention contains 1.10-12.00 mol % of SiO₂ and1.10-12.00 mol % of B₂O₃, for example, 1.20-11.00 mol % of SiO₂ and1.20-10.00 mol % of B₂O₃, or 1.25-10.00 mol % of SiO₂ and 1.25-8.00 mol% of B₂O₃.

According to another aspect, the phosphate laser glass compositionaccording to the invention contains 1.50-8.00 mol % of Nb₂O₅, forexample, 1.60-6.50 mol % of Nb₂O₅, or 1.70-5.50 mol % of Nb₂O₅.

According to another aspect, the phosphate laser glass compositionaccording to the invention contains 1.50-7.00 mol % of Nb₂O₅ and1.10-18.00 mol % of SiO₂, for example, 1.60-6.00 mol % of Nb₂O₅ and1.20-15.00 mol % of SiO₂, or 1.70-4.50 mol % of Nb₂O₅ and 1.25-12.00 mol% of SiO₂.

According to another aspect, the phosphate laser glass compositionaccording to the invention contains 1.50-3.70 mol % of Nb₂O₅, 1.10-18.00mol % of SiO₂ and 1.10-12.00 mol % of B₂O₃, for example, 1.60-3.60 mol %of Nb₂O₅, 1.20-15.00 mol % of SiO₂ and 1.20-11.00 mol % of B₂O₃, or1.70-3.55 mol % of Nb₂O₅, 1.25-12.00 mol % of SiO₂ and 1.25-10.00 mol %of B₂O₃.

In a further aspect, the glass compositions should not contain entitiesthat could lead to crystallization, for example, it was determined thatlevels of Ta₂O₅ above about 1 mol % can lead to crystallization of Ta—Pphases, and as such, high levels of Ta₂O₅ should be avoided from theglasses.

According to another aspect, the phosphate laser glass compositionaccording to the invention exhibits an effective emission bandwidth forYb³⁺ (Δλ_(eff)) of at least 39.50 nm, for example, 40.00-54.00 nm or42.00-54.00 nm or 42.40-53.50 nm and an effective emission bandwidth forNd³⁺ (Δλ_(eff)) of at least 32.00 nm , for example 32.00-36.50 nm or33-35 nm.

According to another aspect, the phosphate laser glass compositionaccording to the invention exhibits an effective emission bandwidth forYb³⁺ (Δλ_(eff)) of at least 39.50 nm, e.g., >40.00 nm or >47.00 nmor >52.00 nm ; and an effective emission bandwidth for Nd³⁺ (Δλ_(eff))of at least 32.00 nm, for example >34.00 nm or >36.00 nm.

In a further embodiment, any of the disclosed glasses may be furthersensitized with transition metals such as Cr, e.g., Cr₂O₃. In someinstances this makes the glasses more useable in a flashlamp pumpedlaser system.

With regards to the additional components, the glass contains a maximumof 4 weight percent, especially a maximum of 2 weight percent, ofconventional additives or impurities, such as refining agents (e.g.,As₂O₃ and Sb₂O₃) and antisolarants (e.g., Nb₂O₅). In addition, the glasscomposition may contain halides to help dry the melt of residual waterand to help in the refining of the glass. For example, the glasscomposition may contain up to 9 wt % F, preferably not more 5 wt %, and,up to 5 wt % Cl, although Cl is less preferred than F.

The glasses according to the invention can also be prepared without alasing ion. For example, the glasses according to the invention preparedwithout a lasing ion can be used as a cladding glass in a laserwaveguide device. Additionally, by doping the glasses according to theinvention with one or more transition metals that introduce absorptionat the lasing wavelength, the resultant transition metal-doped glass canserve as an edge cladding glass in certain laser system designs.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and further details, such as features and attendantadvantages, of the invention are explained in more detail below on thebasis of the exemplary embodiments which are diagrammatically depictedin the drawings, and wherein:

FIG. 1 graphically illustrates the experimental Yb³⁺ emission spectrum(intensity as a function of wavelength), as well as the spectrum derivedfrom curve fitting, for the phosphate laser glass composition ofEXL-7/Yb in accordance with the invention;

FIG. 2 graphically illustrates the Yb³⁺ emission spectra for phosphatelaser glass compositions;

FIG. 3 graphically illustrates the effective bandwidth of Yb³⁺ emissionof phosphate laser glass compositions in accordance with the inventionand prior art phosphate laser glass compositions;

FIG. 4 illustrates a typical emission cross section curve for Yb;

FIG. 5 illustrates a typical emission cross section curve for Nd;

FIG. 6 illustrates effective bandwidth, Δλ_(eff), of emission of EXL Ndlaser glass in comparison with neodymium doped APG-1, APG-2, and IOG-1laser glasses (Judd-Ofelt Results);

In FIG. 2, the Yb³⁺ emission spectra of selective laser glasses areprovided. For comparison purposes, the emission spectra of APG-1/Yb andAPG-2/Yb are presented as representatives of typical phosphate laserglasses. The top data line to the bottom data line (for the majority ofthe data set) are in the following order EXL-2/Yb, EXL-13/Yb, APG-1doped with Yb (Yb:APG-1), and APG-2 doped with Yb (Yb:APG-2).

In the examples of Table 1a and Table 4a, all of the glasses were madeusing laser grade ingredients and melted under dry oxygen environmentwith stirring action using a Pt stir for better homogeneity. Examples onTables 3, 5a, 6a and 7a were prepared in small, <100 cm³, melts thatwere not under a dry oxygen atmosphere or stirred; and, in many cases,were of insufficient quality to allow full property characterization.Where properties could not be measured the entry in the table is “NA”.All of the glasses were cast into molds and appropriately annealed toremove stress. Yb doped glasses were then ground into fine powders usingtungsten carbide grinding cell. Nd doped glasses were prepared as bulkcuvette samples at least nominally 10 mm×10 mm×40 mm in size. A powdersample of each Yb doped glass and a cuvette samples of each Nd dopedglass were used to measure an emission spectrum, from which theeffective emission bandwidth (Δλ_(eff)) was determined according toEquation (1):

$\begin{matrix}{{\Delta \; \lambda_{eff}} = \frac{\int{{I(\lambda)}{\lambda}}}{I_{\max}}} & (1)\end{matrix}$

where the integrated area of the emission spectrum was made between 925and 1100 nm for Yb and from 1000 nm to 1200 nm for Nd and the maximumemission intensity (I_(max)) is found at the wavelength (e.g. λ_(Peak))close to 975 nm for Yb as shown in FIG. 4 and close to 1055 nm for Nd asshown in FIG. 5. For the calculation, raw emission spectra were usedthat had been first curve fitted with a spline function to reduce thenoise level.

Table 2 and FIG. 3 summarize the effective bandwidth results for Ybdoped glasses. The relative bandwidth broadening listed in Table 2 isbased on a comparison of a bandwidth of 38 nm, i.e., the average of thebandwidths for APG-1 ad APG-2. Relative to Δλ_(eff) of APG-1 and APG-2,the newly designed EXL glasses showed significant improvement on bandbroadening, i.e., many EXL glasses have demonstrated the bandwidth widerthan APG-1 and APG-2 glasses by more than 10 nm.

As can be seen in the data presented in FIG. 3, the networkhybridization approach according to the invention provides clearsignificant improvements in Yb bandwidth. The bandwidths presented inFIG. 3 are determined by using the Judd-Ofelt analysis. All of the EXLglasses as shown in FIG. 3 have effective emission bandwidths of about40 nm or larger.

When doping the same glasses as above with Nd, rather than Yb, some ofthe glasses showed improved bandwidths. But, improvement did not occurin all glasses.

Some Nd doped examples used an approach of reducing the amount of P₂O₅(the dominant glass former in all the examples with Yb and Nd). Whilenot being bound to any specific theory, it is believed that based onthese data, that Nd preferentially locates in the glass structure nearP, so even with network hybridization the local environments around Ndare not greatly varied. Lowering the P₂O₅ content in the glasses is thusan attractive path for creating Nd-doped glasses with broader emissionbandwidth.

Two glasses, 21 and 17, were doped with two different rare earths (Erand Pr) in an attempt to better understand what makes emission bandwidthbroader. The latter glass (17) with TeO₂ was heavily colored and couldnot be analyzed for laser properties. But for (21) at least evaluationof emission bandwidth was possible (by both Judd-Ofelt and McCumbermethods) and found that Pr became broader (compared to Pr doped IOG-1,Pr:IOG-1) and that Er became more narrow (again, compared to Er dopedIOG-1, Er:IOG-1).

However, improved results for Nd doped materials, but with a lower P₂O₅range appears to use the network hybridization approach. Preferably, forNd doped glasses as disclosed herein, the P₂O range is 35 to 55 mol %,preferably 40 to 50 mol %, and more preferably 40-48 mol %. Optionally,the SiO₂ content in these glasses is higher, e.g., 8-20 mol %,preferably 10-15 mol %. Further optionally, higher amounts of B₂O₃ areused, for example, about 8-12 mol %, e.g., 10 mol %.

While the examples in Tables 1a, 3a and 4a use SiO₂, B₂O₃, Nb₂O₅, and/orTeO₂ as the other glass formers, other metal oxides can be used as glassformers, such as Bi₂O₃, GeO₂ and/or WO₃, Ln₂O₃ (Ln=La, Nd, Yb, Er, orPr), Al₂O₃ and/or even Sb₂O₃. The particular compositions selected inTable 5a were only doped with Nd, and the results of emission bandwidthwere not particularly broad. However, based on these data, one wouldfully expect that these same glasses doped with Yb would provide a broademission bandwidth.

TABLE 1a Glass Compositions (mol %) of New EXL Laser Glasses ContainingYb₂O₃ Metal Oxide Content Example No. mol % 1/Yb 2/Yb 3/Yb 4/Yb 5/Yb6/Yb 7/Yb 8/Yb 9/Yb P₂O₅ 56.38 49.64 50.49 50.89 50.69 50.49 49.19 55.7049.64 SiO₂ 2.57 1.29 2.51 2.53 B₂O₃ 2.57 1.29 2.57 2.51 Al₂O₃ 4.69 4.134.20 4.24 4.22 4.20 4.09 4.64 4.13 Li₂O 2.780 2.44 2.49 2.51 2.50 2.492.42 2.74 2.44 K₂O 11.93 10.50 10.68 10.77 10.73 10.68 10.41 11.79 10.50Na₂O 8.47 7.46 7.59 7.65 7.62 7.59 7.39 8.37 7.46 MgO 6.17 10.67 7.4310.94 9.18 7.43 10.58 8.19 7.30 CaO 1.89 1.66 1.69 1.70 1.70 1.69 1.651.86 1.66 BaO 3.75 4.96 5.04 1.69 3.37 5.04 1.64 1.85 4.96 TeO₂ 1.462.53 2.57 1.73 2.15 1.71 1.67 1.89 1.69 Yb₂O₃ 1.48 1.51 1.45 1.54 1.491.52 1.46 1.47 1.56 La₂O₃ 0.62 0.78 0.87 2.53 1.70 0.80 0.80 1.09 2.41Nb₂O₅ 3.37 3.46 1.72 3.43 3.34 3.37 Sb₂O₃ 0.39 0.35 0.35 0.35 0.35 0.350.34 0.39 0.35 Total 100.01 100.00 99.99 100.00 100.00 99.99 100.0099.98 100.00 Metal Oxide Content Example No. mol % 10/Yb 11/Yb 12/Yb13/Yb 14/Yb 15/Yb 16/Yb 17/Yb P₂O₅ 50.89 46.50 50.49 49.64 50.89 51.7951.79 51.79 SiO₂ 2.37 2.57 2.59 2.64 2.64 B₂O₃ 2.59 2.37 2.53 2.64 2.64Al₂O₃ 4.24 3.87 4.20 4.13 4.24 4.31 4.31 4.31 Li₂O 2.51 2.29 2.49 2.442.51 2.55 2.55 2.55 K₂O 10.77 9.84 10.68 10.50 10.77 10.96 10.96 10.96Na₂O 7.65 6.99 7.59 7.46 7.65 7.78 7.78 7.78 MgO 7.48 10.00 10.86 10.6710.94 11.13 7.62 7.62 CaO 1.70 1.56 1.69 1.66 1.70 1.73 1.73 1.73 BaO1.69 4.64 5.04 4.96 1.69 1.72 1.72 1.72 TeO₂ 2.59 2.37 1.71 1.69 2.592.64 2.64 1.76 Yb₂O₃ 1.56 1.51 1.43 1.47 1.46 1.42 1.51 1.47 La₂O₃ 2.512.23 0.89 2.50 2.61 0.96 0.87 2.67 Nb₂O₅ 3.46 3.16 3.52 Sb₂O₃ 0.35 0.320.35 0.35 0.35 0.36 0.36 0.36 Total 99.99 100.02 99.99 100.00 99.9999.99 100.00 100.00

TABLE 1b Optical/Thermal/Physical Properties of New EXL Laser GlassesContaining Yb₂O₃ and of Reference Glasses Yb: APG-1 and Yb: IOG-1Optical/Thermal/ Example No. Physical Property 1/Yb 2/Yb 3/Yb 4/Yb 5/Yb6/Yb 7/Yb 8/Yb 9/Yb 10/Yb Refractive Index at 587 nm @ 1.52391 1.560201.53160 1.56187 1.54506 1.55598 1.55072 1.52463 1.56366 1.55940 30C./hr, n_(d) Abbe Number, V_(d) 65.24 54.69 64.99 54.46 59.74 55.9155.89 65.15 54.88 55.03 Density, ρ [g/cm³] 2.759 2.929 2.828 2.921 2.8672.895 2.830 2.752 2.967 2.826 Indentation 0.59 0.53 0.56 0.58 0.56 0.560.59 0.54 0.57 0.59 Fracture Toughness for 3.0N Load, K_(IC) IndentationFracture Toughness for 9.8N Load, K_(IC) Thermal Conductivity @ 0.570.61 0.59 0.62 0.58 0.60 0.62 0.57 0.59 0.61 25 C., K_(25 C.) [W/mK]Thermal Conductivity @ 0.60 0.63 0.62 0.65 0.63 0.64 0.67 0.61 0.63 0.6690 C., K_(90 C.) [W/mK] Poisson Ratio, ν 0.26 0.26 0.26 0.26 0.26 0.260.26 0.26 0.26 0.26 Young's Modulas, E [GPa] 50.3 60.2 56.3 62.2 59.060.3 61.6 54.7 60.5 61.6 Linear Coef. of Thermal 142.3 120.4 135.6 117.3124.6 116.6 116.6 140.3 116.8 115.7 Expansion, α_(20-300 C.) [10⁻⁷/K]Softening Point, T_(sp) [C.] Glass Transition Temperature, 388 428 410446 431 439 450 406 441 457 T_(g) [C.] Knoop Hardness, HK 367 368 376392 362 371 372 339 363 380 α_(3.333 μm) [cm⁻¹] (A measure 0.57 0.480.62 0.39 0.43 0.54 0.50 0.55 0.55 0.51 of residual OH content)α_(3.0 μm) [cm⁻¹] (A measure 0.26 0.29 0.31 0.26 0.26 0.30 0.28 0.270.34 0.29 of residual OH content) Example No. Optical/Thermal/ Yb: Yb:Physical Property 11/Yb 12/Yb 13/Yb 14/Yb 15/Yb 16/Yb 17/Yb APG-1 IOG-1Refractive Index at 587 nm @ 1.56470 1.52920 1.53961 1.53329 1.525661.55109 1.53195 1.52935 1.52060 30 C./hr, n_(d) Abbe Number, V_(d) 54.8365.87 64.86 64.58 65.48 64.30 64.92 68.39 67.61 Density, ρ [g/cm³] 2.8262.824 2.834 2.836 2.760 2.818 2.816 2.622 2.733 Indentation 0.62 0.580.56 0.57 0.56 0.61 0.60 0.84 Fracture Toughness for 3.0N Load, K_(IC)Indentation Fracture Toughness for 9.8N Load, K_(IC) ThermalConductivity @ 0.60 0.59 0.57 0.58 0.60 0.59 0.59 0.81 25 C., K_(25 C.)[W/mK] Thermal Conductivity @ 0.65 0.63 0.62 0.63 0.65 0.64 0.64 0.86 90C., K_(90 C.) [W/mK] Poisson Ratio, ν 0.26 0.26 0.26 0.26 0.26 0.26 0.260.24 Young's Modulas, E [GPa] 63.3 57.6 59.5 58.6 58.0 58.4 57.6 67.1Linear Coef. of Thermal 112.6 132.6 132.6 126.6 126.4 120.9 128.7 97.4Expansion, α_(20-300 C.) [10⁻⁷/K] Softening Point, T_(sp) [C.] 569.8Glass Transition Temperature, 455 415 429 426 420 424 422 475 T_(g) [C.]Knoop Hardness, HK 381 349 358 356 353 384 367 464 α_(3.333 μm) [cm⁻¹](A measure 0.46 0.51 0.57 0.34 0.59 0.69 0.49 1.60 1.31 of residual OHcontent) α_(3.0 μm) [cm⁻¹] (A measure 0.30 0.29 0.33 0.22 0.31 0.36 0.270.97 0.70 of residual OH content)

TABLE 1c Laser Properties of New EXL Laser Glasses Containing Yb₂O₃ andof Reference Glasses Yb: APG-1 and Yb: IOG-1 Example No. Laser Property1/Yb 2/Yb 3/Yb 4/Yb 5/Yb 6/Yb 7/Yb 8/Yb 9/Yb 10/Yb Refractive Index at1.516 1.550 1.524 1.552 1.536 1.546 1.541 1.517 1.554 1.549 1000 nm,n_(1000 nm) Non-linear Refractive 1.15 1.66 1.18 1.68 1.39 1.59 1.561.15 1.67 1.64 Index, n₂ [10⁻¹³ esu] Fluorescence Lifetime, 2459 21612277 2356 2339 2361 2401 2376 2337 2213 τ [msec] Input Yb₂O₃ [wt %] 4.754.75 4.76 4.76 4.74 4.74 4.76 4.76 4.74 4.76 λ_(Peak) ^(p) [nm](Judd-Ofelt) 976.1 975.9 975.9 976.0 975.7 975.9 975.9 975.9 975.9 975.9Δλ_(eff) [nm] (Judd-Ofelt) 48.53 53.47 39.84 45.78 44.71 44.35 45.8744.40 49.56 43.63 Maximum σ_(em) ^(p) [10⁻²⁰ 1.09 0.94 1.26 1.00 0.990.98 1.06 1.08 0.91 1.06 cm²] (Judd-Ofelt) Maximum σ_(em) ^(s) [10⁻²⁰0.78 0.73 0.73 0.63 0.65 0.62 0.71 0.70 0.66 0.68 cm²] (Judd-Ofelt)λ_(Peak) ^(s) [nm] (Judd-Ofelt) 1004.1 1007.8 1004.0 1004.9 1006.41005.9 1005.4 1004.3 1006.0 1003.3 Δλ_(FWHM) [nm] (Judd-Ofelt) 55.0062.30 10.10 11.30 12.50 12.30 11.50 50.60 58.60 10.40 τ_(R) [msec](Judd-Ofelt) 0.99 1.00 1.03 1.10 1.15 1.15 1.04 1.09 1.11 1.09 λ_(Peak)^(p) [nm] (McCumber) 975.6 975.0 975.3 975.2 975.0 974.9 974.7 975.2974.7 974.9 Δλ_(eff) [nm] (McCumber) 16.36 16.85 17.23 18.76 19.96 20.1519.82 19.90 19.60 19.59 Maximum σ_(em) ^(p) [10⁻²⁰ 2.41 2.23 2.18 1.821.66 1.62 1.83 1.80 1.71 1.76 cm²] (McCumber) Maximum σ_(em) ^(s) [10⁻²⁰0.60 0.59 0.58 0.55 0.55 0.54 0.61 0.58 0.55 0.56 cm²] (McCumber)λ_(Peak) ^(s) [nm] (McCumber) 1000.4 1003.5 1001.9 1002.4 1001.6 1003.91002.2 1001.5 1003.0 1003.6 Δλ_(FWHM) [nm] (McCumber) 5.10 5.10 5.406.10 6.60 6.60 6.50 6.50 6.40 6.40 τ_(R) [msec] (McCumber) 1.13 0.931.07 1.39 1.15 1.14 1.05 1.13 1.13 1.12 Radiation Trapping 1.89 1.951.15 1.10 0.97 0.86 1.02 1.01 1.26 1.00 Coefficient, rtc Example No. Yb:Yb: Laser Property 11/Yb 12/Yb 13/Yb 14/Yb 15/Yb 16/Yb 17/Yb APG-1 IOG-1Refractive Index at 1.555 1.521 1.531 1.525 1.518 1.543 1.524 1.5221.513 1000 nm, n_(1000 nm) Non-linear Refractive 1.68 1.15 1.21 1.201.15 1.61 1.18 1.09 1.07 Index, n₂ [10⁻¹³ esu] Fluorescence Lifetime,2169 2392 2915 2217 2731 2795 2863 2150 2542 τ [msec] Input Yb₂O₃ [wt %]4.74 4.76 4.74 4.75 4.75 4.74 4.74 4.75 4.73 λ_(Peak) ^(p) [nm](Judd-Ofelt) 975.9 975.9 976.0 975.9 976.0 976.1 975.9 975.5 976.1Δλ_(eff) [nm] (Judd-Ofelt) 45.09 48.84 50.48 50.25 50.67 48.97 50.1240.09 34.86 Maximum σ_(em) ^(p) [10⁻²⁰ 1.05 0.94 0.91 0.92 0.92 0.950.90 1.10 1.31 cm²] (Judd-Ofelt) Maximum σ_(em) ^(s) [10⁻²⁰ 0.68 0.670.68 0.67 0.70 0.68 0.67 0.64 0.63 cm²] (Judd-Ofelt) λ_(Peak) ^(s) [nm](Judd-Ofelt) 1006.9 1004.6 1006.9 1006.8 1003.7 1005.4 1004.3 1002.71005.1 Δλ_(FWHM) [nm] (Judd-Ofelt) 10.70 57.00 59.80 58.60 59.60 56.6059.20 9.70 8.60 τ_(R) [msec] (Judd-Ofelt) 1.06 1.13 1.12 1.12 1.12 1.091.15 1.18 1.15 λ_(Peak) ^(p) [nm] (McCumber) 974.7 975.0 975.0 974.7974.9 974.9 974.8 974.9 975.5 Δλ_(eff) [nm] (McCumber) 19.67 19.55 19.4519.46 19.30 19.49 19.39 18.71 18.28 Maximum σ_(em) ^(p) [10⁻²⁰ 1.79 1.751.76 1.76 1.81 1.77 1.73 1.76 1.87 cm²] (McCumber) Maximum σ_(em) ^(s)[10⁻²⁰ 0.58 0.55 0.56 0.56 0.57 0.57 0.55 0.56 0.56 cm²] (McCumber)λ_(Peak) ^(s) [nm] (McCumber) 1003.9 1003.3 1002.5 1002.5 1001.1 1002.61002.1 1002.2 1003.2 Δλ_(FWHM) [nm] (McCumber) 6.40 6.40 6.40 6.30 6.306.30 6.30 6.10 6.00 τ_(R) [msec] (McCumber) 1.03 1.14 1.15 1.18 1.141.13 1.19 1.18 1.24 Radiation Trapping 1.00 1.25 1.34 1.33 1.40 1.241.32 0.85 0.61 Coefficient, rtc

TABLE 2 Effective Emission Bandwidth of Yb³⁺ Ions in New EXL PhosphateLaser Glasses Comparing with Existing Phosphate Laser Glasses Lasing ionYb³⁺ Yb₂O₃ Relative Band Broadening Example wt % mol % Δλ_(eff) (nm)(nm) 1 4.75 1.48 48.53 10.64 2 4.75 1.51 53.47 15.59 3 4.76 1.45 39.841.96 4 4.76 1.54 45.78 7.89 5 4.74 1.49 44.71 6.83 6 4.74 1.52 44.356.46 7 4.76 1.46 45.87 7.99 8 4.76 1.47 44.40 6.52 9 4.74 1.56 49.5611.67 10 4.76 1.56 43.63 5.74 11 4.74 1.51 45.09 7.21 12 4.76 1.43 48.8410.96 13 4.74 1.47 50.48 12.60 14 4.75 1.46 50.25 12.37 15 4.75 1.4250.67 12.78 16 4.74 1.51 48.97 11.08 17 4.74 1.47 50.12 12.23 Yb:APG-14.75 1.38 40.09 Ref Yb:APG-2 4.72 1.40 35.67 Ref Yb:IOG-1 4.73 1.5034.86 −3.02

TABLE 3a Cr₂O₃ Sensitized EXL-17 with Yb₂O₃ (mol %) Metal Oxide ContentExample No. mol % 17S/1 17S/2 SiO₂ 2.638 2.639 B₂O₃ 2.638 2.639 P₂O₅51.753 51.771 Al₂O₃ 4.307 4.308 Li₂O 2.548 2.549 Na₂O 7.774 7.777 K₂O10.952 10.956 MgO 7.615 7.617 CaO 1.729 1.729 BaO 1.719 1.719 TeO₂ 1.7591.759 La₂O₃ 2.668 2.669 Yb₂O₃ 1.469 1.469 Cr₂O₃ 0.072 0.036 Sb₂O₃ 0.3600.360

TABLE 3b Optical/Thermal/Physical Properties of Cr₂O₃ Sensitized EXL-17with Yb₂O₃ Example No. Optical/Thermal/Physical Property 17S/1 17S/217/Yb Refractive Index at 587 nm @ 1.53277 1.53283 1.53195 30 C./hr,n_(d) Abbe Number, V_(d) 65.19 64.96 64.92 OH @ 3000 nm 0.344 0.2910.267 OH @ 3333 nm 0.644 0.535 0.487 Density, ρ [g/cm³] 2.819 2.8202.816 Linear Coef. of Thermal Expansion, 124.1 124.1 128.7 α_(20-300C)[10⁻⁷/K] Tg [C.] 429 430 422

TABLE 3c Laser Properties of Cr₂O₃ Sensitized EXL-17 with Yb₂O₃ ExampleNo. Laser Property 17S/1 17S/2 17/Yb Refractive Index at 1000 nm,n_(1000 nm) 1.525 1.525 1.524 Non-linear Refractive Index, 1.18 1.181.18 n₂ [10⁻¹³ esu] Fluorescence Lifetime, τ [msec] 2522 2718 2863 InputYb₂O₃ [wt %] 4.73 4.74 4.74 λ_(Peak) ^(p) [nm] (Judd-Ofelt) 975.3 975.3975.9 Δλ_(eff) [nm] (Judd-Ofelt) 32.24 38.18 50.12 Maximum σ_(em) ^(p)[10⁻²⁰ cm²] 1.28 1.12 0.90 (Judd-Ofelt) Maximum σ_(em) ^(s) [10⁻²⁰ cm²]0.54 0.57 0.67 (Judd-Ofelt) λ_(Peak) ^(s) [nm] (Judd-Ofelt) 1003.51003.3 1004.3 Δλ_(FWHM) [nm] (Judd-Ofelt) 8.0 9.2 59.20 τ_(R) [msec](Judd-Ofelt) 1.25 1.21 1.15 λ_(Peak) ^(p) [nm] (McCumber) 974.7 974.8974.8 Δλ_(eff) [nm] (McCumber) 18.13 18.81 19.39 Maximum σ_(em) ^(p)[10⁻²⁰ cm²] 1.70 1.69 1.73 (McCumber) Maximum σ_(em) ^(s) [10⁻²⁰ cm²]0.51 0.53 0.55 (McCumber) λ_(Peak) ^(s) [nm] (McCumber) 1002.2 1003.11002.1 Δλ_(FWHM) [nm] (McCumber) 6.30 6.4 6.30 τ_(R) [msec] (McCumber)1.67 1.38 1.19 Radiation Trapping Coefficient, rtc 0.43 0.65 1.32

TABLE 4a Glass Compositions (mol %) of New EXL Laser Glasses ContainingNd₂O₃ Metal Oxide Content Example No. mol % 1/Nd 2/Nd 3/Nd 4/Nd 5/Nd6/Nd 7/Nd 8/Nd 9/Nd P₂O₅ 56.38 49.64 50.49 50.89 50.69 50.49 49.19 55.7049.64 SiO₂ 0.00 0.00 2.57 0.00 1.29 0.00 2.51 0.00 2.53 B₂O₃ 0.00 0.002.57 0.00 1.29 2.57 2.51 0.00 0.00 Al₂O₃ 4.69 4.13 4.20 4.24 4.22 4.204.09 4.64 4.13 Li₂O 2.78 2.44 2.49 2.51 2.50 2.49 2.42 2.74 2.44 K₂O11.93 10.50 10.68 10.77 10.73 10.68 10.41 11.79 10.50 Na₂O 8.47 7.467.59 7.65 7.62 7.59 7.39 8.37 7.46 MgO 6.17 10.67 7.43 10.94 9.18 7.4310.58 8.19 7.30 CaO 1.89 1.66 1.69 1.70 1.70 1.69 1.65 1.86 1.66 BaO3.75 4.96 5.04 1.69 3.37 5.04 1.64 1.85 4.96 TeO₂ 1.44 2.53 2.57 1.732.15 1.71 1.67 1.89 1.69 Ta₂O₅ 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.000.00 Nd₂O₃ 0.68 0.60 0.61 0.61 0.61 0.61 0.59 0.67 0.60 La₂O₃ 1.44 1.691.71 3.46 2.58 1.71 1.67 1.89 3.37 Nb₂O₅ 0.00 3.37 0.00 3.46 1.72 3.433.34 0.00 3.37 Sb₂O₃ 0.39 0.35 0.35 0.35 0.35 0.35 0.34 0.39 0.35 Total100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 MetalOxide Content Example No. mol % 10/Nd 11/Nd 12/Nd 13/Nd 14/Nd 15/Nd16/Nd 17/Nd P₂O₅ 50.89 46.50 50.49 49.64 50.89 51.79 51.79 51.79 SiO₂0.00 2.37 2.57 0.00 2.59 0.00 2.64 2.64 B₂O₃ 2.59 2.37 0.00 2.53 0.002.64 0.00 2.64 Al₂O₃ 4.24 3.87 4.20 4.13 4.24 4.31 4.31 4.31 Li₂O 2.512.29 2.49 2.44 2.51 2.55 2.55 2.55 K₂O 10.77 9.84 10.68 10.50 10.7710.96 10.96 10.96 Na₂O 7.65 6.99 7.59 7.46 7.65 7.78 7.78 7.78 MgO 7.4810.00 10.86 10.67 10.94 11.13 7.62 7.62 CaO 1.70 1.56 1.69 1.66 1.701.73 1.73 1.73 BaO 1.69 4.64 5.04 4.96 1.69 1.72 1.72 1.72 TeO₂ 2.592.37 1.71 1.69 2.59 2.64 2.64 1.76 Ta₂O₅ 0.00 0.00 0.00 0.00 0.00 0.000.00 0.00 Nd₂O₃ 0.61 0.56 0.61 0.60 0.61 0.62 0.62 0.62 La₂O₃ 3.46 3.161.71 3.37 3.46 1.76 1.76 3.52 Nb₂O₅ 3.46 3.16 0.00 0.00 0.00 0.00 3.520.00 Sb₂O₃ 0.35 0.32 0.35 0.35 0.35 0.36 0.36 0.36 Total 100.00 100.00100.00 100.00 100.00 100.00 100.00 100.00 Metal Oxide Content ExampleNo. mol % 18/Nd 19/Nd 20/Nd2 21/Nd2 21/Nd P₂O₅ 52.88 47.90 47.88 47.89147.78 SiO₂ 10.00 15.00 10.01 2.43 B₂O₃ 9.994 2.43 Al₂O₃ 5.62 5.62 5.615.617 3.98 Li₂O 5.52 5.49 2.52 2.502 3.98 K₂O 5.76 5.77 5.77 3.772 10.11Na₂O 7.18 MgO 14.95 11.95 9.95 9.928 6.67 CaO 3.69 3.69 3.69 2.707 1.60BaO 3.70 3.70 3.69 2.692 3.18 TeO₂ 2.43 Ta₂O₅ 2.43 Nd₂O₃ 0.62 0.61 0.610.615 0.58 La₂O₃ 1.46 1.46 1.46 1.458 2.43 Nb₂O₅ 5.46 3.46 3.46 2.4572.43 Sb₂O₃ 0.35 0.36 0.36 0.355 0.33 Total 100.00 100.00 100.00 100.00100.00

TABLE 4b Optical/Thermal/Physical Properties of New EXL Laser GlassesContaining Nd₂O₃ and of Reference Glasses Nd: APG-1 and Nd: IOG-1Optical/Thermal/ Example No. Physical Property 1/Nd 2/Nd 3/Nd 4/Nd 5/Nd6/Nd 7/Nd 8/Nd 9/Nd 10/Nd Refractive Index at 587 nm @ 1.52642 1.562841.53379 1.56490 1.54926 1.56038 1.55473 1.52676 1.56687 1.56405 30C./hr, n_(d) Abbe Number, V_(d) 64.65 54.39 64.23 54.37 59.08 54.9655.31 64.92 54.72 54.20 Density, ρ [g/cm³] 2.736 2.895 2.800 2.894 2.8482.879 2.806 2.727 2.943 2.888 Indentation 0.538 0.561 0.649 0.581 0.6190.569 0.623 0.566 0.591 0.581 Fracture Toughness for 3.0N Load, K_(IC)Indentation Fracture Toughness for 9.8N Load, K_(IC) ThermalConductivity @ 0.57 0.61 0.58 0.60 0.58 0.59 0.62 0.58 0.58 0.60 25 C.,K_(25 C.) [W/mK] Thermal Conductivity @ 0.60 0.64 0.63 0.65 0.65 0.670.67 0.62 0.62 0.69 90 C., K_(90 C.) [W/mK] Poisson Ratio, ν 0.26 0.260.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 Young's Modulas, E [GPa] 52.8860.38 56.01 61.78 58.81 59.28 60.60 54.30 60.37 61.19 Linear Coef. ofThermal 144.5 123.7 141.0 115.8 126.0 126.0 122.9 137.8 120.5 117Expansion, α_(20-300 C.) [10⁻⁷/K] Glass Transition Temperature, 392 429409 441 426 429 442 403 443 445 T_(g) [C.] Knoop Hardness, HK 328.7358.5 347.1 371.4 362.7 358.3 379.8 343.7 357.3 375.4 α_(3.333 μm)[cm⁻¹] (A measure 1.19 0.74 0.73 0.36 0.75 0.81 0.62 0.89 0.38 0.51 ofresidual OH content) α_(3.0 μm) [cm⁻¹] (A measure 0.55 0.42 0.37 0.250.40 0.42 0.34 0.43 0.25 0.29 of residual OH content) Optical/Thermal/Example No. Physical Property 11/Nd 12/Nd 13/Nd 14/Nd 15/Nd 16/Nd 17/Nd18/Nd 19/Nd 20/Nd2 Refractive Index at 587 nm @ 1.56905 1.53429 1.542621.53702 1.53138 1.55591 1.53550 1.58419 1.56319 1.55630 30 C./hr, n_(d)Abbe Number, V_(d) 54.89 64.75 64.83 64.51 57.07 54.40 64.66 48.05 53.8363.03 Density, ρ [g/cm³] 2.962 2.819 2.887 2.810 2.749 2.814 3.110 2.8852.8245 2.782 Indentation 0.573 0.552 0.569 0.588 0.558 0.530 0.572 0.6730.699 0.678 Fracture Toughness for 3.0N Load, K_(IC) IndentationFracture Toughness for 9.8N Load, K_(IC) Thermal Conductivity @ 0.600.58 0.58 0.55 0.56 0.55 0.56 0.63 0.63 0.62 25 C., K_(25 C.) [W/mK]Thermal Conductivity @ 0.65 0.63 0.64 0.64 0.65 0.65 0.65 0.73 0.74 0.7490 C., K_(90 C.) [W/mK] Poisson Ratio, ν 0.26 0.26 0.26 0.26 0.26 0.260.26 0.25 0.25 0.24 Young's Modulas, E [GPa] 62.25 56.99 59.80 58.7658.31 58.44 58.16 68.13 65.61 62.62 Linear Coef. of Thermal 116.9 134.6136.2 130.6 139.9 127.4 133.5 83.6 89.1 79.1 Expansion, α_(20-300 C.)[10⁻⁷/K] Glass Transition Temperature, 450 408 429 423 420 428 427 477479 518 T_(g) [C.] Knoop Hardness, HK 374.5 342.6 352.3 364.4 353.8357.2 363.9 424.0 460.7 401.1 α_(3.333 μm) [cm⁻¹] (A measure 0.66 0.440.47 0.69 0.93 0.40 0.51 0.43 0.40 0.48 of residual OH content)α_(3.0 μm) [cm⁻¹] (A measure 0.40 0.25 0.29 0.39 0.47 0.23 0.28 0.280.27 0.31 of residual OH content) Optical/Thermal/ Example No. PhysicalProperty 21/Nd2 EXL-21/Nd Nd: APG-1 Nd: IOG-1 Refractive Index at 587 nm@ 1.54955 1.53269 1.52490 30 C./hr, n_(d) Abbe Number, V_(d) 57.43 67.867.5 Density, ρ [g/cm³] 2.731 C 2.607 2.718 Indentation 0.81 R 0.83Fracture Toughness for 3.0N Load, K_(IC) Indentation Y 0.91 FractureToughness for 9.8N Load, K_(IC) Thermal Conductivity @ 0.64 S 0.79 25C., K_(25 C.) [W/mK] Thermal Conductivity @ 0.77 T 0.86 90 C., K_(90 C.)[W/mK] Poisson Ratio, ν 0.24 A 0.25 Young's Modulas, E [GPa] 67.25 L66.75 Linear Coef. of Thermal 71.7 S 99.3 Expansion, α_(20-300 C.)[10⁻⁷/K] Glass Transition Temperature, 562 P, Ta, Nb 457 T_(g) [C.]Knoop Hardness, HK 492.7 And 433.8 α_(3.333 μm) [cm⁻¹] (A measure 1.14P, Ta 1.28 of residual OH content) α_(3.0 μm) [cm⁻¹] (A measure 0.620.64 0.46 of residual OH content)

TABLE 4c Laser properties of New EXL Laser Glasses Containing Nd₂O₃ andof Reference Glasses Nd: APG-1 and Nd: IOG-1 Example No. Laser Property1/Nd 2/Nd 3/Nd 4/Nd 5/Nd 6/Nd 7/Nd 8/Nd 9/Nd Refractive Index at 1.5181.552 1.525 1.554 1.540 1.55 1.544 1.518 1.556 1054 nm, n_(1054 nm)Non-linear Refractive 1.17 1.69 1.21 1.70 1.43 1.65 1.61 1.16 1.69Index, n₂ [10⁻¹³ esu] Fluorescence Lifetime, 378.5 369.9 386.8 377.4383.0 377.5 380.5 385.4 376.9 τ [μsec] Input Nd₂O₃ [wt %] 1.88 1.62 1.721.63 1.67 1.63 1.66 1.87 1.57 Peak Emission Wavelength, 1053.1 1053.91053.5 1054.0 1054.0 1054.5 1054.6 1053.7 1054.7 λ_(Peak) [nm] EffectiveEmission Bandwidth, 22.47 22.68 25.21 26.08 25.33 27.20 28.64 24.9527.88 Δλ_(eff) [nm] Maximum Emission Cross 4.03 4.01 4.00 3.82 3.95 3.613.44 4.18 3.55 Section, σ_(em) [cm²] FWHM Emission Bandwidth, 18.8021.00 20.60 21.90 21.90 22.70 22.70 20.90 22.40 Δλ_(FWHM) [nm] RadiativeLifetime, τ_(Rad) (μsec) 387 366 347 337 342 346 345 339 339 Judd-OfeltParameter, 3.46 3.89 4.32 4.82 4.54 4.54 4.77 4.29 4.61 Ω₂ [10⁻²⁰ cm²]Judd-Ofelt Parameter, 4.27 4.36 4.64 4.55 4.60 4.46 4.56 4.81 4.50 Ω₄[10⁻²⁰ cm²] Judd-Ofelt Parameter, 5.00 4.81 5.56 5.35 5.44 5.29 5.325.78 5.31 Ω₆ [10⁻²⁰ cm²] Example No. Laser Property 10/Nd 11/Nd 12/Nd13/Nd 14/Nd 15/Nd 16/Nd 17/Nd Refractive Index at 1.553 1.558 1.5261.534 1.528 1.523 1.545 1.527 1054 nm, n_(1054 nm) Non-linear Refractive1.70 1.70 1.20 1.22 1.21 1.20 1.65 1.20 Index, n₂ [10⁻¹³ esu]Fluorescence Lifetime, 377.5 371.5 380.6 379.2 382.5 383.6 380.5 386.1 τ[μsec] Input Nd₂O₃ [wt %] 1.61 1.51 1.74 1.66 1.72 1.80 1.69 1.73 PeakEmission Wavelength, 1054.5 1054.8 1055.0 1054.9 1054.2 1054.0 1053.51053.7 λ_(Peak) [nm] Effective Emission Bandwidth, 26.81 30.78 27.1527.24 26.28 26.83 26.31 25.69 Δλ_(eff) [nm] Maximum Emission Cross 3.613.21 3.78 3.63 3.87 3.79 3.83 3.44 Section, σ_(em) [cm²] FWHM EmissionBandwidth, 22.90 23.70 21.30 22.80 22.40 22.40 20.90 22.00 Δλ_(FWHM)[nm] Radiative Lifetime, τ_(Rad) (μsec) 348 339 342 351 343 346 338 395Judd-Ofelt Parameter, 4.68 4.74 4.42 4.46 4.61 4.49 4.65 3.98 Ω₂ [10⁻²⁰cm²] Judd-Ofelt Parameter, 4.42 4.50 4.71 4.51 4.67 4.69 4.58 4.04 Ω₄[10⁻²⁰ cm²] Judd-Ofelt Parameter, 5.19 5.27 5.65 5.42 5.59 5.62 5.474.88 Ω₆ [10⁻²⁰ cm²] Example No. Laser Property 18/Nd 19/Nd 20/Nd2 21/Nd221/Nd Nd: APG-1 Nd: IOG-1 Refractive Index at 1.572 1.552 1.547 1.5401.525 1.525 1054 nm, n_(1054 nm) Non-linear Refractive 2.16 1.72 1.331.50 1.11 1.11 Index, n₂ [10⁻¹³ esu] Fluorescence Lifetime, 370.4 380.7391.8 392.4 c 353.9 359.4 τ [μsec] Input Nd₂O₃ [wt %] 1.67 1.77 1.751.80 r 2.96 2.05 Peak Emission Wavelength, 1055.3 1054.6 1053.7 1054.7 y1054.3 1053.4 λ_(Peak) [nm] Effective Emission Bandwidth, 32.33 33.2528.71 34.73 s 28.44 24.78 Δλ_(eff) [nm] Maximum Emission Cross 2.92 2.773.15 2.37 t 3.68 3.91 Section, σ_(em) [cm²] FWHM Emission Bandwidth,25.20 25.30 24.00 26.60 a 23.3 21.70 Δλ_(FWHM) [nm] Radiative Lifetime,τ_(Rad) (μsec) 347 366 372 416 l 331 364.28 Judd-Ofelt Parameter, 5.134.97 5.37 5.64 s 4.43 4.55 Ω₂ [10⁻²⁰ cm²] Judd-Ofelt Parameter, 4.334.21 4.24 3.86 5.05 4.51 Ω₄ [10⁻²⁰ cm²] Judd-Ofelt Parameter, 4.96 4.944.86 4.42 5.68 5.37 Ω₆ [10⁻²⁰ cm²]

TABLE 5a Examples prepared with Nd (mol %), where other glass formersBiO₃, GeO₂ and WO₃ are used Metal Oxide Example No. Metal Oxide MetalOxide Content 17/Nd Content Example No. Content Example No. mol %(baseline) 22/Nd 23/Nd mol % 24/Nd 25/Nd mol % 26/Nd 27/Nd P₂O₅ 51.7945.00 45.00 P₂O₅ 45.00 45.00 P₂O₅ 45.00 45.00 SiO₂ 2.64 10.00 5.00 SiO₂10.00 5.00 SiO₂ 10.00 5.00 B₂O₃ 2.64 10.00 5.00 B₂O₃ 10.00 5.00 B₂O₃10.00 5.00 Al₂O₃ 4.31 4.31 4.31 Al₂O₃ 4.31 4.31 Al₂O₃ 4.31 4.31 Li₂O2.55 2.55 3.85 Li₂O 2.55 3.85 Li₂O 2.55 3.85 K₂O 10.96 6.76 10.96 K₂O6.76 10.96 K₂O 6.76 10.96 Na₂O 7.78 7.78 7.78 Na₂O 7.78 7.78 Na₂O 7.787.78 MgO 7.62 7.62 7.62 MgO 7.62 7.62 MgO 7.62 7.62 CaO 1.73 0.00 0.00CaO 0.00 0.00 CaO 0.00 0.00 BaO 1.72 0.00 0.00 BaO 0.00 0.00 BaO 0.000.00 TeO₂ 1.76 0.00 2.00 TeO₂ 0.00 2.00 TeO₂ 0.00 2.00 Bi₂O₃ 0.00 3.006.00 GeO₂ 3.00 6.00 WO₃ 3.00 6.00 Nd₂O₃ 0.62 0.62 0.62 Nd₂O₃ 0.62 0.62Nd₂O₃ 0.62 0.62 La₂O₃ 3.52 2.00 1.50 La₂O₃ 2.00 1.50 La₂O₃ 2.00 1.50Sb₂O₃ 0.36 0.36 0.36 Sb₂O₃ 0.36 0.36 Sb₂O₃ 0.36 0.36 Total 100.00 100.00100.00 Total 100.00 100.00 Total 100.00 100.00

TABLE 5b Optical Properties of Examples prepared with Nd, where otherglass formers BiO₃, GeO₂ and WO₃ are used Example No. Optical Property22/Nd 23/Nd 24/Nd 25/Nd 26/Nd 27/Nd Refractive index at 587 nm @ 30C./hr, n_(d) 1.561 NA 1.534 NA 1.54034 1.54612 Abbe Number, V_(d) NA NANA NA NA 58.48 Density, ρ [g/cm³] 2.943 NA 2.727 NA 2.792  2.885Appearance glass ceramic glass part glass glass ceramic Color brownishopaque brownish opaque bluish brownish

TABLE 5c Laser Properties of Examples prepared with Nd, where otherglass formers BiO₃, GeO₂ and WO₃ are used Example No. Laser Property22/Nd 23/Nd 24/Nd 25/Nd 26/Nd 27/Nd Refractive Index at 1054 nm,n_(1054 nm) NA NA NA NA NA NA Non-linear Refractive Index, n₂ [10⁻¹³esu] NA NA NA NA NA NA Fluorescence Lifetime, τ [μsec] NA NA NA NA NA NAInput Nd₂O₃ [wt %] 1.74 NA 1.91 NA 1.85 NA Peak Emission Wavelength,λ_(Peak) [nm] 1054.1 NA 1053.1 NA 1053.6 NA Effective EmissionBandwidth, Δλ_(eff) [nm] 28.53 NA 33.24 NA 28.20 NA Maximum EmissionCross Section, σ_(em) [cm²] 3.30 NA 2.61 NA 3.53 NA FWHM EmissionBandwidth, Δλ_(FWHM) [nm] 23.7 NA 25.2 NA 23.6 NA Radiative Lifetime,τ_(Rad) (μsec) 313 NA 339 NA 317 NA Judd-Ofelt Parameter, Ω₂ [10⁻²⁰ cm²]2.90 NA 3.50 NA 4.64 NA Judd-Ofelt Parameter, Ω₄ [10⁻²⁰ cm²] 6.70 NA6.94 NA 5.79 NA Judd-Ofelt Parameter, Ω₆ [10⁻²⁰ cm²] 4.24 NA 3.77 NA4.92 NA

TABLE 6a Examples (mol %) with Pr instead of Yb or Nd Metal OxideContent Example No. mol % 17/Pr 21/Pr P₂O₅ 51.79 47.89 SiO₂ 2.64 10.00B₂O₃ 2.64 10.00 Al₂O₃ 4.31 5.62 Li₂O 2.55 4.96 K₂O 10.96 3.77 Na₂O 7.780.00 MgO 7.62 9.94 CaO 1.73 2.70 BaO 1.72 2.69 TeO₂ 1.76 0.00 Nb₂O₅ 0.000.00 Pr₂O₃ 0.62 0.61 La₂O₃ 3.52 1.46 Sb₂O₃ 0.36 0.35 Total 100.00 100.00

TABLE 6b Optical Properties of Examples with Pr instead of Yb or Nd andreference Pr:IOG-1 Example No. Optical Property Pr:IOG-1 17/Pr 21/PrRefractive Index 1.5256 1.53507 1.53329 at 587 nm @ 30 C./hr, n_(d) AbbeNumber, NA NA NA V_(d) Density, ρ 2.728 2.792 2.696 [g/cm³] Appearanceglass glass glass Color lt. green brownish lt. green

TABLE 6c Laser Properties of Examples with Pr instead of Yb or Nd andreference Pr:IOG-1 Example No. Laser Property 17/Pr 21/Pr Pr:IOG-1λ_(lower) [nm] NA 478.2 478.5 λ_(upper) [nm] NA 492.9 489.6 Δλ_(FWHM)[nm] NA 14.70 11.10 λ_(Peak) [nm] NA 480.9 481.2 Δλ_(eff) [nm] NA 14.4912.15

TABLE 7a Examples (mol %) with Er instead of Yb or Nd Metal OxideContent Example No. mol % 17/Er 21/Er P₂O₅ 51.79 47.89 SiO₂ 2.64 10.00B₂O₃ 2.64 10.00 Al₂O₃ 4.31 5.62 Li₂O 2.55 4.96 K₂O 10.96 3.77 Na₂O 7.780.00 MgO 7.62 9.94 CaO 1.73 2.70 BaO 1.72 2.69 TeO₂ 1.76 0.00 Nb₂O₅ 0.000.00 Er₂O₃ 0.62 0.61 La₂O₃ 3.52 1.46 Sb₂O₃ 0.36 0.35 Total 100.00 100.00

TABLE 7b Optical Properties of Examples with Er instead of Yb or Nd andreference Er:IOG-1 Example No. Optical Property Er:IOG-1 17/Er 21/ErRefractive Index 1.523 1.53457 1.53149 at 587 nm @ 30 C/hr, n_(d) AbbeNumber, 67.28 65.10 66.99 V_(d) Density, ρ 2.721 2.804 2.695 [g/cm³]Appearance glass glass glass Color pink brown/pink pink

TABLE 7c Laser Properties of Examples with Er instead of Yb or Nd andreference Er:IOG-1 Example No. Laser Property 17/Er 21/Er Er:IOG-1λ_(lower) [nm] NA 1527.2 1526.6 λ_(upper) [nm] NA 1550.0 1556.6Δλ_(FWHM) [nm] NA 22.80 30.00 λ_(Peak) [nm] NA 1533.9 1533.5 Δλ_(eff)[nm] NA 40.80 49.15

The entire disclosure[s] of all applications, patents and publications,cited herein, are incorporated by reference herein.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A laser phosphate glass having the composition in mol % of P₂O₅ 35-65SiO₂  0-20 B₂O₃  0-15 Al₂O₃ >0-10 Nb₂O₅  0-10 TeO₂  0-5 GeO₂  0-5 WO₃ 0-5 Bi₂O₃  0-5 La₂O₃  0-5 Ln₂O₃ >0-10 (Ln = lasing ions of elements 58through 71 in the periodic table) R₂O 10-30 (R = Li, Na, K, Rb, Cs) MO10-30 (M = Mg, Ca, Sr, Ba, Zn) Sb₂O₃  0-5

and wherein SiO₂, B₂O₃, TeO₂, Nb₂O₅, Bi₂O₃, WO₃, and/or GeO₂, arepresent from >0 to about 15 mol % each, with their sum being at least 1mol %.
 2. A laser phosphate glass according to claim 1 having thecomposition in mol % of P₂O₅ 40.00-65.00 SiO₂  0.00-18.00 B₂O₃ 0.00-12.00 Al₂O₃ 2.00-8.00 Li₂O  0.00-20.00 K₂O  0.00-20.00 Na₂O 0.00-20.00 MgO  0.00-15.00 CaO 0.00-5.00 BaO  0.00-15.00 TeO₂ 0.00-5.00Nd₂O₃ 0.50-3.00 and/or Yb₂O₃ La₂O₃ 0.00-5.00 Nb₂O₅ 0.00-5.00 Sb₂O₃0.00-2.00

wherein the composition contains at least 1.00 mol % of TeO₂, SiO₂, B₂O₃or Nb₂O₅, or a combination thereof.
 3. A laser phosphate glass accordingto claim 1 having the composition in mol % of P₂O₅ 49.00-57.00 SiO₂ 0.00-10.00 B₂O₃ 0.00-5.00 Al₂O₃ 2.00-6.00 Li₂O  1.00-18.00 K₂O 1.00-18.00 Na₂O  0.00-10.00 MgO  1.00-12.00 CaO 0.00-3.00 BaO 1.00-12.00 TeO₂ 0.00-4.00 Yb₂O₃ 1.00-2.50 La₂O₃ 0.50-3.00 Nb₂O₅0.00-4.00 Sb₂O₃ 0.20-0.50

wherein the composition contains at least 1.00 mol % of TeO₂, SiO₂, B₂O₃or Nb₂O₅, or a combination thereof.
 4. A glass according to claim 1,which has a Δλ_(eff) that is higher than the Δλ_(eff) of the otherwisesame glass with the exception of the absence of SiO₂, B₂O₃, TeO₂, Nb₂O₅,Bi₂O₃, WO₃, and/or GeO₂ from said glass.
 5. A glass according to claim1, which contains Yb only as the rare earth dopant, and has a Δλ_(eff)that is at least 38 nm evaluated by the lineshape function technique ina Judd-Ofelt analysis.
 6. A glass according to claim 1, which containsYb only as the rare earth dopant, and has a Δλ_(eff) that is 40.0 nm to54.00 nm evaluated by the lineshape function technique in a Judd-Ofeltanalysis.
 7. A glass according to claim 1, which contains Nd only as therare earth dopant, and has a Δλ_(eff) that is at least 32 nm evaluatedby the lineshape function technique in a Judd-Ofelt analysis.
 8. A glassaccording to claim 7, which contains 45 to 50 mol % P₂O₅.
 9. A glassaccording to claim 1, which contains Nd only as the rare earth dopant,and has a Δλ_(eff) that is 32.00 nm to 36.50 nm evaluated by thelineshape function technique in a Judd-Ofelt analysis.
 10. A glassaccording to claim 1, further comprising one or more additives,impurities, refining agents, antisolarants and/or halides.
 11. A glassaccording to claim 1, which contains Pr as the rare earth dopant.
 12. Ina solid state laser system comprising a solid gain medium and a pumpingsource, the improvement wherein said solid gain medium is a glass havinga composition in accordance with claim
 1. 13. A laser system accordingto claim 12, wherein the power output of system is at least a pettawattor greater.
 14. A method for generating a laser beam comprisingflashlamp pumping or diode pumping a glass according to claim
 1. 15. Amethod for lowering the nonlinear refractive index and/or lowering thethermal expansion of a glass according to claim 1 that contains Nd asthe rare earth dopant, comprising replacing at least some of said Ndwith Yb, and optionally further replacing at least some of the Latherein with Yb, and optionally adding further Yb.
 16. A method forbroadening the emission bandwidth of a aluminophosphate laser glassdoped with a rare earth ion, comprising introducing at least 2 mol % ofone or more non-phosphate network formers into the glass, wherein saidnetwork formers are selected from the group consisting of SiO₂, B₂O₃,TeO₂, Nb₂O₅, Bi₂O₃, WO₃, and/or GeO₂.